[BUG] :get return invalid digit format after :decr

Environment

• Memcache (Docker) memcached:1.5.16-alpine
• Erlang OTP 24.1
• Elixir 1.13.1
  • {:memcachex, "~> 0.5.4"}

Examples

iex(1)> Memcache.set(pid, "a", "10")
{:ok}
iex(2)> Memcache.decr(pid, "a")      
{:ok, 9}
iex(3)> Memcache.get(pid, "a") 
{:ok, "9 "}

iex(1)> Memcache.set(pid, "a", "100")
{:ok}
iex(2)> Memcache.decr(pid, "a")
{:ok, 99}
iex(3)> Memcache.get(pid, "a")
{:ok, "99 "}

This one is a little more "nice-to-have" than my other request, but I'm posting it for your consideration.

Currently cas/4 only works on cache items that already exist. It would be convenient if a :default opttion were supported, to make a "create-or-atomic-update" workflow possible.

If the initial get fails to find the requested key, we could then check opts for a :default key and set that instead.

This functionality is possible to implement with a function that wraps cas/4 in user code, but I thought I'd put the suggestion out there to add built-in support to the library. Thanks.

Hello!

Telemetry is getting traction now that it's included in Phoenix and Ecto out-of-the-box. What's your stance on emitting telemetry events from this library? Would you welcome contributions?

It would allow users of this library to capture important metrics and send them to their monitoring solution. This way, we save everyone the time to instrument their own usage of this library.

Stephan

Apologies for the additional open issue—just wondering what your usual schedule is for publishing new releases.

I would like to use the new cas/4 options in some code that I am working on now, but if you would like to wait on cutting a release, I can work around that. Thanks!

There's a type mismatch when using an encoder like Json or Erlang as the typespecs for set/add/replace are defined as binary() instead of term(). For example, in the unit tests:

assert {:ok} == Memcache.set(pid, "hello", ["list", 1])

Conflicts with the set/4 definition of binary in the third parameter:

  @doc """
  Sets the key to value
  Accepted options: `:cas`, `:ttl`
  """
  @spec set(GenServer.server(), binary, binary, Keyword.t()) :: store_result
  def set(server, key, value, opts \\ []) do
    ...

When calling dialyzer in an app that uses the Erlang encoder we get:

The call 'Elixir.Memcache':add
         (_name@1 :: atom(),
          _key@1 :: any(),
          _data@1 ::
              #{'ts' := 'nil' | integer(),
                'ttl' := 'nil' | integer(),
                'value' := _},
          [{'ttl', integer()}, ...]) breaks the contract
          ('Elixir.GenServer':server(),
          binary(),
          binary(),
          'Elixir.Keyword':t()) ->
             store_result()

Hello again!

Memcachex is not compatible with Dalli, even if both of them are using JSON as the serializer. The reason is that Dalli will only run the deserialize if a certain bit is set on the flags of the key. Here's the relevant code:

Only deseralize if bit is set:
https://github.com/petergoldstein/dalli/blob/master/lib/dalli/server.rb#L442

Set serialization bit if a serializer is used:
https://github.com/petergoldstein/dalli/blob/master/lib/dalli/server.rb#L435

I'm not entirely sure, but I think the fix would be to set that bit in the flags on the set, add, and replace commands (if a coder is specified).

What do you think?

Currently, Memcache.cas/4 does not accept a :ttl option like most of the other functions that set cache keys. Can support be added, where the :ttl value gets passed through to the set_cas/5 call?

I'd be happy to post a PR for this change. Thanks for providing such a great library with quality docs!

question - why is this not compatible with latest Poison 5.0 version?

We use mcrouter for our memcache setup, but unfortunately it only supports ascii protocol.

I'm thinking of writing an ascii protocol implementation for Memcachex; is something that y'all would be onboard with?

It would be great if you can put a more comprehensive readme file to help understand how to use your memcached client with elixir.

Hi

I'm using memcache's increment but it is not working after a get.

iex(3)> Memcache.incr(Worker, "my_key")
{:ok, 3}
iex(4)> Memcache.get(Worker, "my_key")
** (ArgumentError) argument error
    :erlang.binary_to_term("3")
    (memcachex) lib/memcache/coder/erlang.ex:9: Memcache.Coder.Erlang.decode/2
    (memcachex) lib/memcache.ex:488: Memcache.decode_response/2

Maybe the value is not encoded on incr and decr?

=== UPDATE ===
I'm using Erlang coder, when I change to JSON it works.

Hi. The hexdocs for the project show a module Memcache.Cluster and Memcache.Cluster.Hash, but I can't find them in the source code.

Does this client support memcached clusters with the same consistent hashing algorithm as the Ruby clients (Dalli, Memcache)?

Thanks for the info!

Can you add support for these two operations?

I'm currently writing a higher level memcached client (support for clusters, fetch, mfetch, Ecto integration) that uses your client under the hood and I need mget and mset in order for mfetch to be efficient.

Thank you.